FIGURE 3.

Inhibition of ¹²⁵I-FH19–20 binding to C3d with mutant constructs. Binding of the fluid-phase ¹²⁵I-FH19–20 to plastic surface-coated C3d was inhibited using serial dilutions of the unlabeled FH19–20 mutants. After washing, radioactivity was detected with a γ-counter and the results were fitted to inhibition curves. The results are shown in two panels. A, the mutants that bound to C3b similarly to the wild-type FH19–20; B, the mutants that showed decreased binding. Results of a representative experiment are shown. C, for each FH19–20 construct IC₅₀ value was calculated from three independent experiments performed in duplicate. Standard deviations for IC₅₀ are presented as error bars. Labels for the aHUS-associated mutations are in bold; cpm, counts per minute; *, p < 0.05; ●, FH19–20 (wild-type); ○, D1119G; ■, D1119G/Q1139A; □, Q1139A; ▴, W1157L; ▾, T1184R; +, L1189R; ♦, R1206A; Δ, R1210A; and ▿, R1215Q.